Piston



E. E. ALLYNE.

PISTON.

APPLICATiON FILED JAN. 9. I919- 1 A2 6 1 38, Patented Aug. 15, 1922.

I To all whom it may concern:

EDMUND E. ALLYNE, OFv CLEVELAND, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, Tb

ALUMINUM MANUFAGTURES, INCORIEORATED, F CLEVELAND, OHIO, A CORPO- RATION OF DELAWARE.

PISTON.

Specification of Letters Patent. Pate t d A 15 192% Application filed January 9,1919. Serial No. 270,318.' I

Be it known that LEDMUND E. ALLYNE, a citizen of the United States, residing at Cleveland, in the county of C'uyahoga-and State of Ohio, have invented certain new and useful Improvements in Pistons, of

which the following is a specification, reference being had therein to the accompanying drawings.

This invention relates to improvements in pistons for internal combustion engines and to the process of producing said pistons. It relates especially to pistons made of aluminum alloys or other light weight metalswhich are subject in operation to corrosion resulting in so called pittingf.

The principal object of the invention is the production of pistons of materials of the character referred to which will be substantially unaffected by those operating conditions which cause pitting of-pistons of such materials heretofore used.

I To this end I provide the piston made of aluminum alloy, or other material subject to pitting, with a protective layer or coatingof material, preferably metal, which is not subject to corrosion under the conditions of operation. The pitting action is -usually localized, affecting only' certain parts of the top or side piston surfaces which are exposed to the gases of the combustion chamber, and in the practice of my invention it is necessary to provide the protective coating only for those parts which are found to be-subject to the pitting action.

In order that my invention may be clearly understood I will describe in detail its application to pistons of aluminum alloy.

In the carrying out of my improved method of making pistons the first step is the production of an aluminum alloy pistonof the desired form and construction in any known manner, for example by casting, machining and finishing.

The next step is to determine whether such piston will be subject to corrosion in the particular engine in which-it 1s to be used, cur. As has been indicated above, the pitting action is more or less definitely localized. Several theories have been advancedand if s0, where the corrosion will 00- gases or a softening or melting of the metal,

andthe mechanical action of localized currents of the combustion gases as they enter or leave the cylinder or during combustion.

Whatever the true explanation may be, it is difficult to predict whether or not the p1stons of a particularengine will be subject-to pitting and where the pitting will appear, if it does occur. In some cases the location of the pitting seems to bear a certaln relation to the spark plug or the in-.

take passage, or both. In other cases no such definite casual. relation can be perceived. The only satisfactory and sure way to determine this is to make an actual trial of the. engine under the most severe operating conditions. If pitting occurs, its location is thus determined and my improved protective coating can then be applied to the pistons to be used in the same and similar engines so as to cover and protect the area-or areas where pitting would occur.

The location of the pitting having been determined, in one way or another, the next step of my improvedprocess is the applibeen secured with iron, nickel and copper.

Any one of these metals can be used or any two or more of such metals. For example, a coating may consist of iron covered with copper, or iron covered with nickel, or of other various combinations of these or other suitable metals. As I am at present advised, the best results are obtained from a coating composed of a layer of iron upon which is superposed a layer of nickel.

The coating may be of any thickness suitable to insure protection of the underlying metal subject to corrosion and may be apwhere light weight is a desideratum the plied in any suitable manner. Obviously necessary to afiord the desired protection. In many cases a coating of iron or iron and nickel from onethousandth to two thousandths of an inch in thickness is found to afford adequate protection. I

While, as stated above, the protective coating may be applied to the piston in any suitable manner, the fact that only a portion of thepiston'surface need betreated, as well as other considerations, make the electrolytic depositions of the coating especially advantageous. In applying the coating by this method the area to be covered is first-cleaned and polished and otherwise treated as may be necessary for the reception of a firm and adherent coating of the material. The piston is then placed in the plating tank and the metal or metals deposited thereon in a well known manner. The piston is then removed from the plating bath and all'depositedmetal' removed except that which covers the -area to be protected. The removal of this extra metal is accompanying drawings a piston construct-- ed in accordance with my invention to obviate' the pitting which has been found to occur in one-type of engine. In the drawings, Figs. 1 and 2 are .a side elevation and plan, respectively, ofa piston embodying my improvements.

Fig. 3 is a transverse vertical section through the upper part of a cylinder of an internal combustion engine with one of my improved pistons shown in elevation. t is a horizontal section on the line 4-4., Fig. 3.

Fig. 5 is a verti 5-5, Fig. 3.

The plston illustrated in Figs. 1 and 2 is of the type used in the Liberty aviation motor. It is cast from aluminum alloy and comprises a head section 1 having a top surface 1 and a side surface 1", a skirt 2, and pin bosses 3, 3. 4, 4c are the usual packing rings.

. he piston has a portion of its top wall 1 and of its side wall 1 provided with a protective coating 5, preferably of iron and nickel electrolytlcally deposited as herein above described.

In Fig. 3 the piston-is shown mounted'in cal sec tion on the line the engine cylinder 6. The cylinder is promeasles passage 8 and a spark plug 9. In this par ticular type of-engine it was found that pitting'of the aluminum alloy pistons occurred in a region adjacent the intake passage and the sparkplug and it will be observed that the protective coating covers this part of the piston.

While it seems probable that the pitting of aluminum alloy pistons is due to oxidation or other corrosive chemical action by the combustion gases, some who have studied the matter incline to the View that the pitting results from a melting of the alloy, or at least of the eutectic portion of the alloy, due to exceedingly high temperatures in the combusion chamber, such melting or softening of the metal being followed by the erosive or disintegrating action of the gas currents on thesoftened metal. In this connectionit will be observed that the coating metals which ll have herein above specified for use on aluminum alloy pistons, haveconsiderably higher melting points than does the aluminum alloy so that my invention provides an effective remedy for pitting whether it results from chemical action or an actual melting of the metal, or from both of these actions.

It is to be noted that whereas certain of the various specified coating metals may not be entirely resistant to corrosion when they alone comprise acomplete piston, they are all rendered noncorrodible when intimately attached to an aluminum alloy piston as herein disclosed. Although the true reason for this result is not definitely known to me, I believe it to'be due to the maintename of the coating metal at a comparatively low temperature. Aluminum and its alpossess all of the desired properties of pistons'of this character and are at the same time free from the harmful pitting action to which such pistons are subject.

It will be understood that while the invention is especially useful in connection .with pistons of aluminum alloy or the like,

in its. broader aspects it is not limited tosuch materials but is applicableto any piston material subject to corrosive pitting to which a non-corrodible protective coating can, be applied. It will also be understood loys absorb and conduct heat more. rapidly than many metals, such for example as iron. Accordingly an aluminum alloy piston will .thatthe method .of applying the protective coating can be Widely varied and that the foregoing description and the accompanying drawings have een set forth for purpose of explanation and illustration and are not intended to define the scope of the invention.

What I claim is:

1. A piston for internal combustion enines composed of aluminum alloy and havmg on that part exposed to the combustion gases means for protecting the aluminum alloy' from the corrosive action of said gases, said means comprising a coating of irfim intimately united to the aluminum a 0 2. A piston for internal combustion engines composed of aluminum alloy and having on that part exposed to the combustion gases means for protecting the aluminum alloy from the corrosive action of said gases, said means comprising a coating of electrolytically deposited iron intimately united to the aluminum alloy of the piston. In testimony whereof I hereunto aflix my signature.

EDMUND E. ALLYNE. 

